﻿98 
  COLLECTIONS 
  PKOM 
  MELANDSLA.. 
  

  

  22. 
  Petricola 
  lapicida. 
  

  

  Venus 
  lapicida, 
  Chemnitz, 
  Con.-Cab. 
  x. 
  p. 
  356, 
  figs. 
  1664-5 
  ; 
  Soiverhy, 
  

   Conch. 
  Icon. 
  (I'etricola) 
  figs. 
  22, 
  24 
  ; 
  Martens 
  in 
  Von 
  der 
  Deckeri's 
  

   Heisen 
  in 
  Ost-Afrika, 
  vol. 
  iii. 
  p. 
  66, 
  pi. 
  3, 
  figs. 
  3 
  a, 
  b. 
  

  

  Hah. 
  West 
  Indies 
  {Chemnitz, 
  cVOrhigny, 
  Sfc); 
  North 
  Australia 
  

   (/. 
  B. 
  Elsey 
  in 
  Brit. 
  Mus.) 
  ; 
  West 
  Island, 
  Prince 
  of 
  Wales 
  Channel, 
  

   Torres 
  Straits 
  {Copping 
  cr) 
  ; 
  Zanzibar 
  {Peters, 
  teste 
  Martens). 
  

  

  This 
  and 
  the 
  Venus 
  divaricata 
  of 
  Chemnitz 
  I 
  regard 
  as 
  one 
  species, 
  

   and 
  from 
  his 
  description 
  of 
  the 
  former 
  it 
  seems 
  probable 
  that 
  he 
  had 
  

   before 
  him 
  specimens 
  which 
  to 
  a 
  great 
  extent 
  had 
  lost 
  the 
  fine 
  zigzag 
  

   sculpture 
  mentioned 
  in 
  his 
  description 
  of 
  the 
  latter. 
  The 
  raised 
  

   oblique 
  ridges 
  from 
  the 
  umbones 
  down 
  the 
  posterior 
  slope 
  have 
  

   various 
  degrees 
  of 
  development 
  in 
  different 
  specimens, 
  in 
  some 
  existing 
  

   onty 
  near 
  the 
  posterior 
  margin 
  of 
  the 
  valves, 
  whilst 
  in 
  others 
  they 
  

   extend 
  the 
  whole 
  distance 
  from 
  the 
  beaks 
  downwards, 
  and, 
  again, 
  in 
  

   young 
  shells 
  they 
  may 
  be 
  altogether 
  wanting. 
  These 
  ridges 
  are 
  

   easily 
  removed, 
  and 
  seem 
  to 
  be 
  superimposed 
  upon 
  the 
  zigzag 
  sculp- 
  

   ture 
  beneath. 
  After 
  a 
  careful 
  examination 
  of 
  Austrahau 
  specimens 
  

   and 
  others 
  from 
  the 
  West 
  Indies, 
  I 
  cannot 
  detect 
  any 
  material 
  

   specific 
  difi"erences. 
  

  

  The 
  example 
  figured 
  by 
  Dr. 
  E. 
  von 
  Martens 
  as 
  P. 
  divaricata 
  is 
  

   unsually 
  peaked 
  at 
  the 
  umbones. 
  

  

  23. 
  Psammobia 
  modesta. 
  

  

  Deshayes, 
  Proc. 
  Zool. 
  Soc. 
  1854, 
  p. 
  319 
  ; 
  Peeve, 
  Conch. 
  Icon. 
  tig. 
  3. 
  

  

  Hah. 
  Port 
  Jackson 
  {Coppinger) 
  ; 
  Moreton 
  Bay 
  {DesJiayes). 
  

  

  The 
  single 
  specimen 
  before 
  me 
  is 
  rather 
  narrower 
  than 
  that 
  

   figured 
  in 
  the 
  ' 
  Conchologia 
  Iconica.' 
  is 
  purplish 
  lilac 
  within 
  for 
  the 
  

   most 
  part, 
  yellowish 
  near 
  the 
  muscular 
  scars, 
  and 
  exibits 
  the 
  j^inkish 
  

   rays 
  on 
  the 
  ventral 
  margin. 
  The 
  epidermis 
  is 
  brightish 
  yellow. 
  

   Oblique 
  striae 
  are 
  sometimes 
  present 
  at 
  the 
  central 
  portion 
  of 
  the 
  

   valves, 
  but 
  are 
  not 
  conspicuous. 
  

  

  24. 
  Psammobia 
  gracilenta. 
  (Plate 
  VII. 
  figs. 
  B-B 
  2.) 
  

  

  Shell 
  concentrically 
  striated, 
  transversely 
  elongate, 
  very 
  inequi- 
  

   lateral, 
  almost 
  twice 
  as 
  long 
  as 
  high, 
  not 
  very 
  compressed, 
  dirty 
  

   whitish 
  with 
  a 
  few 
  diaphanous 
  zones 
  and 
  several 
  light 
  reddish 
  

   narrow 
  rays 
  beneath 
  a 
  thin 
  pale 
  yellowish-olive 
  epidermis, 
  very 
  

   narrowly 
  gaping 
  at 
  both 
  ends. 
  Anterior 
  dorsal 
  margin 
  of 
  the 
  valves 
  

   about 
  twice 
  as 
  long 
  as 
  the 
  posterior, 
  subrectilinear, 
  and 
  nearly 
  

   parallel 
  with 
  the 
  ventral. 
  Hinder 
  dorsal 
  edge 
  oblique, 
  a 
  little 
  

   arcuate. 
  Lower 
  margin 
  straightish, 
  obliquely 
  curving 
  upward 
  in 
  

   front 
  and 
  more 
  sharply 
  turning 
  at 
  the 
  opposite 
  extremity. 
  Interior 
  

   bluish 
  white, 
  iridescent, 
  exhibiting 
  the 
  reddish 
  rays. 
  Beaks 
  small, 
  

   adjacent, 
  posteriorly 
  inclined. 
  Ligament 
  short, 
  but 
  prominent, 
  placed 
  

   on 
  a 
  conspicuous 
  ligamental 
  plate 
  in 
  each 
  valve 
  behind 
  the 
  umbones. 
  

   A 
  second 
  minute 
  ligament 
  exists 
  immediately 
  in 
  front 
  of 
  them 
  and 
  

  

  